The present invention is a method for the preparation of tertiary-hydrocarbylsilyl compounds. The method comprises contacting a mixture comprising diethylene glycol dibutyl ether, and a Grignard reagent comprising a tertiary-hydrocarbylsilyl group with a silicon compound in the presence of a copper compound. The present invention provides a method for making sterically hindered organosilicon intermediates useful in the pharmaceutical industry.
It is known that copper cyanide as a catalyst in tetrahydrofuran or diethyl ether may be used to prepare sterically hindered tertiary-hydrocarbylsily compounds. However copper cyanide is a known irritant that is highly toxic and presents several environmental hazards.
Shirahata, U.S. Pat. No. 5,068,386, teaches a method for the preparation of tert-hydrocarbylsilyl compounds by reacting a Grignard reagent with a silicon compound in the presence of a cyano compound or a thiocyanate compound. The major drawback with this method is that the catalysts used are highly toxic and are irritants.
Kubota et al., U.S. Pat. No. 5,294,727, teach a method for preparing a tertiary hydrocarbon-silyl compound prepared by reacting a hydrogen halogenosilane, in which hydrogen and halogen atoms are directly bonded to the silicon atom, with a tertiary alkyl Grignard reagent in the presence of a copper compound and/or a quaternary ammonium salt. This method is to preparing the less sterically hindered Si-H containing chlorosilanes.
The present invention provides a method for preparing highly sterically hindered tertiary-hydrocarbylsilyl compounds using a Grignard reagent in the presence of a copper compound avoiding many of the above discussed problems. In addition, the method provides for a two-phase system from which the tertiary-hydrocarbylsilyl compound can be easily separated. Furthermore, the present method provides a substantial reduction in the amount of solvent used and increases the production equipment volumetric efficiency resulting in decreased production cost. The tertiary-hydrocarbylsilyl compounds prepared by the present method are useful, for example, as intermediates in the preparation of silylating agents, steroids and prostaglandins.